[Boatanchors] SSB and carrier insertion?

[Eugene Hertz]

Here's my question. I've begun studying for my general and I read in the arrl book that inserting a carrier with one side band in not a legal emission. Is that right? Could I have misread this? If I read that right, can anyone explain why if DSB with carrier (am) is allowed and LSB and USB without carrier, why wouldnt LSB-C or USB-C (with carrier) be allowed? 

As soon as I get my general and code passed, my transmitter is a central electronics 100V (courtesy W0YVA). This radio has SSB and also SSB with carrier inserted modes (also has PM, AM, FSK, you name it!) and I began to wonder was this kind of emission legal at one time (radio was made around 1959) ? Does any one know when/why it became illegal? 

Also, what would be the benefit of running SSB with carrier? Does it make the signal more easily detected? say, without the need for a product detector, but just a BFO? 

Thanks in advance (for being patient with all my questions!) 
Eugene 
KC2NWG